Use of outpatient parenteral antimicrobial therapy for transrectal ultrasound-guided prostate biopsy prophylaxis in the setting of community-associated multidrug-resistant Escherichia coli rectal colonization

OBJECTIVE

To study the use of ertapenem delivered in an outpatient parenteral antimicrobial therapy (OPAT) hospital-based unit setting for targeted transrectal ultrasound-guided prostate biopsy (TRUSPBx) prophylaxis in the setting of multidrug-resistant (MDR) Escherichia coli rectal colonization. E coli is the pathogen most commonly associated with post-TRUSPBx complications, and there is increasing prevalence of community-associated MDR E coli.

METHODS

Prospective data analysis of all patients admitted to the OPAT unit for administration of intravenous antibiotics for prophylaxis for TRUSPBx over 18-month period was performed. Patients had identification of MDR E coli in rectal swab cultures and/or intolerance to available oral agents. Microbiologic data and tolerability of administered antibiotics and outcome after TRUSPBx were tabulated.

RESULTS

Nine patients (median age 74 years) were referred because of antibiotic-resistant E coli from rectal swabs (all fluoroquinolone resistant, 7 MDR). All patients received ertapenem 1 g intravenously 1 day before TRUSPBx and the day of the procedure before TRUSPBx. None of the patients experienced infectious complications immediately after TRUSPBx or several weeks or months later, and no patient was lost to urologic follow-up.

CONCLUSION

Increasing worldwide reports of prostatitis, urinary tract infections, and septicemia after TRUSPBx because of MDR E coli suggest rectal screening before procedure may be useful in decreasing complications. Targeted prophylaxis in these instances is necessary. Although carbapenems are used for treatment, they are not routinely used for prophylaxis. We report successful use of ertapenem delivered in a hospital-based OPAT unit for TRUSPBx prophylaxis.

Betabox: a beta particle imaging system based on a position sensitive avalanche photodiode

A beta camera has been developed that allows planar imaging of the spatial and temporal distribution of beta particles using a 14 × 14 mm(2) position sensitive avalanche photodiode (PSAPD). This camera system, which we call Betabox, can be directly coupled to microfluidic chips designed for cell incubation or other biological applications. Betabox allows for imaging the cellular uptake of molecular imaging probes labeled with charged particle emitters such as (18)F inside these chips. In this work, we investigate the quantitative imaging capabilities of Betabox for (18)F beta particles, in terms of background rate, efficiency, spatial resolution, and count rate. Measurements of background and spatial resolution are considered both at room temperature (21 °C ± 1 °C) and at an elevated operating temperature (37 °C ± 1 °C), as is often required for biological assays. The background rate measured with a 4 keV energy cutoff is below 2 cph mm(-2) at both 21 and 37 °C. The absolute efficiency of Betabox for the detection of (18)F positron sources in contact with a PSAPD with the surface passivated from ambient light and damage is 46% ± 1%. The lower detection limit is estimated using the Rose Criterion to be 0.2 cps mm(-2) for 1 min acquisitions and a 62 × 62 µm(2) pixel size. The upper detection limit is approximately 21 000 cps. The spatial resolution at both 21 and 37 °C ranges from 0.4 mm FWHM at the center of the field of view (FOV), and degrades to 1 mm at a distance of 5 mm away from center yielding a useful FOV of approximately 10 × 10 mm(2). We also investigate the effects on spatial resolution and sensitivity that result from the use of a polymer based microfluidic chip. For these studies we place varying layers of low-density polyethylene (LDPE) between the detector and the source and find that the spatial resolution degrades by ∼180 µm for every 100 µm of LDPE film. Sensitivity is reduced by half with the inclusion of ∼200 µm of additional LDPE film. Lastly, we demonstrate the practical utilization of Betabox, with an imaging test of its linearity, when coupled to a polydimethylsiloxane microfluidic chip designed for cell based assays.

Safety trial of Floseal(®) haemostatic agent in head and neck surgery

INTRODUCTION

Floseal® (Baxter, Hayward, CA, US) can be of value in reducing blood loss and haematoma rates. The manufacturer’s warnings include allergic reaction, poor wound healing and intravascular thrombosis. We aimed to determine whether Floseal® is safe to use in various head and neck surgery (HNS) procedures.

METHODS

A prospective trial was conducted using Floseal® in 42 various consecutive head and neck surgery procedures. Adverse incidents were used as the main outcome measure, including allergic reaction, wound breakdown, wound infection and thrombosis. Secondary outcome measures included haematoma formation, hospital stay, drain times and output.

RESULTS

No adverse incidents were recorded in the trial period. Two patients developed haematomas and required surgical exploration where a bleeding vessel was identified and dealt with.

CONCLUSIONS

Floseal® is safe to be used in head and neck surgery with no adverse effects. A larger number and a control group are required to ascertain its value in reducing blood loss, haematoma formation, drain usage and hospital stay.

Characterization of a high-resolution hybrid DOI detector for a dedicated breast PET/CT scanner

The aim of this study is to design and test a new high-resolution hybrid depth of interaction (DOI) detector for a dedicated breast PET/CT scanner. Two detectors have been designed and built. The completed detectors are based on a 14 × 14 array of 1.5 × 1.5 × 20 mm(3) unpolished lutetium orthosilicate scintillation crystals, with each element coated in a 50 μm layer of reflective material. The detector is read out from both ends using a position-sensitive photomultiplier tube (PSPMT) and a large active area (20 × 20 mm(2)) avalanche photodiode (APD) to enable acquisition of DOI information. Nuclear instrumentation modules were used to characterize the detectors' performances in terms of timing, intrinsic spatial resolution (ISR) and energy resolution, as well as DOI resolution with a dual-ended readout configuration. Measurements with the APD were performed at a temperature of 10 °C. All crystals were identified at all depths, even though the signal amplitude from the PSPMT decreases with depth away from it. We measured a timing resolution of 2.4 ns, and an average energy resolution of 19%. The mean ISR was measured to be 1.2 mm for crystals in the central row of the array for detectors in the face-to-face position. Two off-center positions were measured corresponding to 26° and 51° oblique photon incidence, and the mean ISR at these positions was 1.5 and 1.7 mm, respectively. The average DOI resolution across all crystals and depths was measured to be 2.9 mm (including the beam width of 0.6 mm). This detector design shows good promise as a high-resolution detector for a dedicated breast PET/CT scanner.

Response of large area avalanche photodiodes to low energy x rays

For an experiment to study neutron radiative beta-decay, we operated large area avalanche photodiodes (APDs) near liquid nitrogen temperature to detect x rays with energies between 0.2 keV and 20 keV. Whereas there are numerous reports of x ray spectrometry using APDs at energies above 1 keV, operation near liquid nitrogen temperature allowed us to reach a nominal threshold of 0.1 keV. However, due to the short penetration depth of x rays below 1 keV, the pulse height spectrum of the APD become complex. We studied the response using monochromatic x ray beams and employed phenomenological fits of the pulse height spectrum to model the measurement of a continuum spectrum from a synchrotron. In addition, the measured pulse height spectrum was modelled using a profile for the variation in efficiency of collection of photoelectrons with depth into the APD. The best results are obtained with the collection efficiency model.

18F-fluorodeoxyglucose positron emission tomography/computed tomography in the assessment of occult primary head and neck cancers--an audit and review of published studies

AIMS

To assess the value of 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with squamous cell and undifferentiated cancer neck nodes and no primary site on conventional assessment.

MATERIALS AND METHODS

Seventy-eight patients with neck nodal metastases from an unknown primary cancer were studied. PET/CT was carried out in all patients, 1h after FDG injection.

RESULTS

Uptake suspicious of an occult primary cancer was found in 46/78 (59.0%) patients. Subsequent investigations confirmed a primary site in the base of the tongue in 14, pharyngeal palatine tonsil in 14, post cricoid in one, lung in one. PET/CT diagnosed primary cancers in 30/78 patients (38.5%); sensitivity, specificity, positive predictive value, negative predictive value: 30/30 (100.0%), 32/48 (66.7%), 30/46 (65.2%), 32/32 (100.0%), respectively. PET/CT detected additional disease in four patients: contralateral nodal disease in two, mediastinal nodal disease in one and liver metastases in one.

CONCLUSIONS

FDG PET/CT is of value in the assessment of patients with occult head and neck primary cancers. However, false-positive results remain a limitation of the investigation.

P2-13-03: Comparative Assessment of 636 Women at Risk for Hereditary Breast Cancer within 3 Public Hospitals: The Consortium of Underserved BRCA Testers

Background: Underserved women at risk for Hereditary Breast and Ovarian Cancer (HBOC) are confronted with many unique challenges, such as barriers to accessing appropriate genetic testing and counseling services and decreased resources, that place them at increased cancer risk. It is unclear whether these high-risk women are appropriately referred for genetic counseling and what their genetic test results demonstrate due to minimal practice-based evidence. To study this population, and to establish an infrastructure to further explore long-term outcomes, we formed the Consortium of Underserved BRCA testers in October 2010 from: San Francisco General Hospital (SF), Stroger Hospital of Cook County (Chicago), and Grady Memorial Hospital (Atlanta).

Methods: Using common clinical and research protocols and mixed methods analysis, we examined and compared referral patterns, demographics, and BRCA test results between sites. We used chart reviews and common data collection instruments to gather and pool data. Using descriptive and comparative statistics, we examined similarities and differences between Consortium sites.

Results: SF's program began 9 years ago, Chicago's began 6 years ago, and Atlanta's began 3 years ago. Medicaid funding for BRCA testing has been available in SF since 2011, in Chicago since 2009, and is not yet available in Atlanta. P values were all <0.05 for comparing referral sources between sites. Each site uses unique referral tools and systems. For example, in SF, a family history screening questionnaire is administered during mammography; in Chicago, an extensive primary care network has been educated to provide appropriate referrals; in Atlanta, a pedigree assessment tool is employed by referring clinics.

Signal and noise properties of position-sensitive avalanche photodiodes

After many years of development, position-sensitive avalanche photodiodes (PSAPDs) are now being incorporated into a range of scintillation detector systems, including those used in high-resolution small-animal PET and PET/MR scanners. In this work, the signal, noise, signal-to-noise ratio (SNR), flood histogram and timing resolution were measured for lutetium oxyorthosilicate (LSO) scintillator arrays coupled to PSAPDs ranging in size from 10 to 20 mm, and the optimum bias voltage and working temperature were determined. Variations in the SNR performance of PSAPDs with the same dimensions were small, but the SNR decreased significantly with increasing PSAPD size and increasing temperature. Smaller PSAPDs (10 mm and 15 mm in width) produced acceptable flood histograms at 24 °C, and cooling lower than 16 °C produced little improvement. The optimum bias voltage was about 25 V below the break down voltage. The larger 20 mm PSAPDs have lower SNR and require cooling to 0-7 °C for acceptable performance. The optimum bias voltage is also lower (35 V or more below the break down voltage depending on the temperature). Significant changes in the timing resolution were observed as the bias voltage and temperature varied. Higher bias voltages provided better timing resolution. The best timing resolution obtained for individual crystals was 2.8 ns and 3.3 ns for the 10 mm and 15 mm PSAPDs, respectively. The results of this work provide useful guidance for selecting the bias voltage and working temperature for scintillation detectors that incorporate PSAPDs as the photodetector.

Pseudo-lyre sign

Carotid body tumours cause characteristic splaying of the internal and external carotid arteries, known as ‘Lyre Sign’. Vagal paragangliomas are rare tumours that arise from glomus cells along the length of the vagus nerve. We present a case in which a vagal paraganglioma has arisen from the vagus nerve at the carotid bifurcation, and has mimicked the ‘Lyre Sign’ of a carotid body tumour.

Tapered LSO arrays for small animal PET

By using detectors with good depth encoding accuracy (∼2 mm), an animal PET scanner can be built with a small ring diameter and thick crystals to simultaneously obtain high spatial resolution and high sensitivity. However, there will be large wedge-shaped gaps between detector modules in such a scanner if traditional cuboid crystal arrays are used in a polygonal arrangement. The gaps can be minimized by using tapered scintillator arrays enabling the sensitivity of the scanner to be further improved. In this work, tapered lutetium oxyorthosilicate (LSO) arrays with different crystal dimensions and different combinations of inter-crystal reflector and crystal surface treatments were manufactured and their performance was evaluated. Arrays were read out from both ends by position-sensitive avalanche photodiodes (PSAPDs). In the optimal configuration, arrays consisting of 0.5 mm LSO elements could be clearly resolved and a depth of interaction resolution of 2.6 mm was obtained for a 20 mm thick array. For this tapered array, the intrinsic spatial is degraded from 0.67 to 0.75 mm compared to a standard cuboidal array with similar dimensions, while the increase in efficiency is 41%. Tapered scintillator arrays offer the prospect of improvements in sensitivity and sampling for small-bore scanners, without large increases in manufacturing complexity.

Repeat-pulse 13CO2 labeling of canola and field pea: implications for soil organic matter studies

Both the quantity and quality of plant residues can impact soil properties and processes. Isotopic tracers can be used to trace plant residue decomposition if the tracer is homogeneously distributed throughout the plant. Continuous labeling will homogeneously label plants but is not widely accessible because elaborate equipment is needed. In order to determine if the more accessible repeat-pulse labeling method could be used to trace plant residue decomposition, this labeling procedure was employed using (13)CO(2) to enrich field pea and canola plants in a controlled environment. Plants were exposed weekly to pulses of 33 atom% (13)CO(2) and grown to maturity. The distribution of the label throughout the plant parts (roots, stem, leaves, and pod) and biochemical fractions (ADF and ADL) was determined. The label was not homogeneously distributed throughout the plant; in particular, the pod fractions were less enriched than other fractions indicating the importance of continuing labeling well into plant maturity for pod-producing plants. The ADL fraction was also less enriched than the ADF fraction. Because of the heterogeneity of the label throughout the plant, caution should be applied when using the repeat-pulse method to trace the fate of (13)C-labeled residues in the soil. However, root contributions to below-ground C were successfully determined from the repeat-pulse labeled root material, as was (13)C enrichment of soil within the top 15 cm. Canola contributed more above- and below-ground residue C than field pea; however, canola was also higher in ADF and ADL fractions indicating a more recalcitrant residue.

A study of the timing properties of position-sensitive avalanche photodiodes

In this paper, we study position-dependent timing shifts and timing resolution in position sensitive avalanche photodiodes (PSAPDs) and their effects on the coincidence window used in positron emission tomography (PET) systems using these devices. There is a delay in PSAPD signals that increases as the excitation position moves from the corner to the center of the device and the timing resolution concurrently worsens. The difference in timing between the center and the corner can be up to 30.7 ns for a 14 x 14 mm(2) area PSAPD. This means that a PSAPD-based PET system could require a very wide coincidence timing window (>60 ns) if this effect is not corrected, although the individual crystal pairs still have full-width half-maximum (FWHM) timing resolutions better than 7.4 ns. In addition to characterizing the timing properties of PSAPDs, two correction methods were developed and applied to data from a pair of PSAPD detectors. These two timing offset corrections reduced the timing shift of a crystal pair from 52.4 ns to 9.7 ns or 1.3 ns, improved the FWHM timing resolution of the detector pair from 24.6 ns to 9.5 ns or 6.0 ns and reduced the timing window (sufficient to cover at least twice the FWHM for all crystal pairs) from 65.1 ns to 22.0 ns or 15.2 ns, respectively. A two-step timing alignment method is proposed for a PET system consisting of multiple PSAPDs. Lastly, the effect of PSAPD size on the timing performance was also evaluated.

Experimental characterization and system simulations of depth of interaction PET detectors using 0.5 mm and 0.7 mm LSO arrays

Small animal PET scanners may be improved by increasing the sensitivity, improving the spatial resolution and improving the uniformity of the spatial resolution across the field of view. This may be achieved by using PET detectors based on crystal elements that are thin in the axial and transaxial directions and long in the radial direction, and by employing depth of interaction (DOI) encoding to minimize the parallax error. With DOI detectors, the diameter of the ring of the PET scanner may also be decreased. This minimizes the number of detectors required to achieve the same solid angle coverage as a scanner with a larger ring diameter and minimizes errors due to non-collinearity of the annihilation photons. In this study, we characterize prototype PET detectors that are finely pixelated with individual LSO crystal element sizes of 0.5 mm x 0.5 mm x 20 mm and 0.7 mm x 0.7 mm x 20 mm, read out at both ends by position sensitive avalanche photodiodes (PSAPDs). Both a specular reflector and a diffuse reflector were evaluated. The detectors were characterized based on the ability to clearly resolve the individual crystal elements, the DOI resolution and the energy resolution. Our results indicate that a scanner based on any of the four detector designs would offer improved spatial resolution and more uniform spatial resolution compared to present day small animal PET scanners. The greatest improvements to spatial resolution will be achieved when the detectors employing the 0.5 mm x 0.5 mm x 20 mm crystals are used. Monte Carlo simulations were performed to demonstrate that 2 mm DOI resolution is adequate to ensure uniform spatial resolution for a small animal PET scanner geometry using these detectors. The sensitivity of such a scanner was also simulated using Monte Carlo simulations and was shown to be greater than 10% for a four ring scanner with an inner diameter of 6 cm, employing 20 detectors per scanner ring.